# A052621 (b-file synthesized from sequence entry)
0 2
1 1
2 2
3 6
4 48
5 120
6 720
7 5040
8 80640
9 362880
10 3628800
11 39916800
12 958003200
13 6227020800
14 87178291200
15 1307674368000
16 41845579776000
17 355687428096000
18 6402373705728000
19 121645100408832000
20 4865804016353280000